In vitro, telomerase can disassociate from the primer following addition of each nucleotide or during the translocation step. The regulation of telomerase disassociation from the telomere in vivo is not well-characterized. One factor that may be involved is a helicase termed hPIF1, which can unanneal the telomerase RNA/telomeric DNA hybrid (Boule et al., 2005; Zhang et al., 2006).